A good boyfriend needs to be a good friend. Yes, guys often tend to forget that a good relationship should start and end with friendship. That is when it will last forever. Be her friend. But, make sure you are not crude. Like her other friends can tell her that she looks like crap straight in the face. You, on the other hand, will have to be a little bit more diplomatic about it. Be open to her weird wacky ideas and allow her to expose the child in her. If you let her be herself completely, she will reciprocate in the best way possible. You can come up with some cute nicknames for girlfriend to show her that you love the cute side of her as well.
Be romantic, but don't overdo it. Today's girls love their prince charming. However, you cannot ignore the fact that they have hectic routines too. Don't smother her with love when she is busy working on a tight deadline. However, you can show much more affection by just sending her a text that you miss her and wish her all the best in finishing her work as fast as possible. It is a thin line that you need to be conscious about. Remember the episode in Friends, wherein Ross lands up at Rachel's office with a picnic? Well, it didn't go well, did it? So, beware of overdoing it. But steer clear from not doing anything either. She needs to know that you are there, around, but not in her hair.
Do not be jealous and possessive. While caring and a slightly protective nature is completely fine with girls, jealousy about her friends is absolutely not. Give her space with her friends, even if it includes her ex-boyfriend. Realize that it is her world that she needs to retain to maintain her sanity. More so, if you get overtly jealous and possessive, it will give her the impression that you don't trust her. That is simply insulting. If you have any reservations about her being with unknown people (the protective nature of the man in you), then ask her to introduce you to her friends. In fact, meeting her friends and getting along with them will work in your favor. However, be very careful to avoid flirting with any of her friends even in the slightest way. Trust me, it won't go down well. Take help on how to deal with jealousy and possessiveness.
Realize that men and women are different. That will never change. So, don't try to change her and make her more like you. Let her be the way she is. If you like a girl, but wish to change her when you get into a relationship with her, then I strongly suggest you stay away from her. You are allowed to give her suggestions, guidance and protect her when she allows you to. But, trying to manipulate and change her is just not right. The rules applies for women as well. Love her for what she is. Love her with her flaws and in spite of them. This, my friend, will be reciprocated to you in the most loving manner possible.